The present invention relates to rotary fluid pumps or compressors, and more particularly to a rotary fluid pump or compressor wherein a rotor is eccentrically mounted within a stator housing and co-operates with the inner peripheral wall of the stator housing and with suitable end wall structure to form suction, compression and delivery chambers so as to produce compressed air or vacuum.
One of the present inventors previously introduced a rotary fluid pump of the type in which a pair of flexible diaphragm type sealing plates are hermetically clamped on the opposite ends of a stator housing by end wall structures to be pressed against the opposite end faces of a rotor driven within the pump cavity to increase the volumetric efficiency of the pump. In use of the rotary fluid pump to ensure the volumetric efficiency of the pump, it is necessary that the flexible sealing plates are constantly pressed against the opposite end faces of the rotor by difference between internal pressure produced within the pump cavity and external pressure applied to the outside faces of the sealing plates.
One of the problems experienced in development of such a pump is that the end-face sealing contacts of the sealing plates against the opposite end faces of the rotor cannot be obtained during rotation of the pump at a low speed. Namely, it is only when the pump is rotated at a high speed say over 1,500 r.p.m., that the necessary high vacuum of over -650 mmHg is obtainable.